Mingo is free for personal use.
"I always used to use Robo3T because of the speed but it's lacking so many features that I'm trying to find the more powerful version of it. But all the alternatives (including Studio3T even) are so slow and sluggish. Mingo was an unexpected breath of fresh air after trying like 6 mongo GUI's :-)"
"Love the interface for creating an index! The mix of WYSIWYG and code is really cool and helpful. :)"
"You have solved those things that annoy me on Robo 3T. Good job."